1. Field of the Invention
The present invention relates generally to a seamless wireless video transmission for multimedia applications, and more particularly, to a temporal error concealment (TEC) method for concealing a temporal error of an image frame caused by a missing macroblock.
2. The Prior Arts
Image transmission service including video meeting, website browsing, image file transmission, is a very important service provided by communication and IT enterprises. Typically, an original image file desired to be transmitted is often too large to be effectively transmitted over the internet, or often occupies too much memory space of the storage device. As such, an image file is often performed with a coding process with a high compression ratio and a low loss ratio before transmission for reducing the size of the image data. Such a coding process may be selected from TIFF, JPEG, MJEP, MPEG, H.264/AVC, in accordance with the demands of the system for the image compression ratio, the loss ratio, so as to obtain an optimal algorithm for static images or continuous images.
However, when being transmitted, the encoded image file is often interfered by the transmission interface or the electrical system of the receiving end. Such interferences usually cause damages or errors of the image file data, so that the receiving end becomes incapable of decoding and recovering the encoded image file back to original by a predetermined corresponding decoding method.
In accordance with psychology of vision, an individual edge would not affect visional recognition. However, such an individual edge may be mutually affected with edges adjacent thereto so as to generate a composition effect. In this concern, human vision is more sensitive to edge distortions. Generally, edge distortions include blurred edges and newly created false edges. As such, it is very important to maintain original edges and avoid the creation of false edges when executing an image process.
A method of recovering or obtaining image data of a missing macroblock according to image data of correct macroblocks of a same frame of the missing macroblock is generally called the SEC method.
There are many algorithms of conventional technologies have been proposed for SEC, such as bilinear interpolation (BI), directional interpolation (DI), and best neighborhood matching (BNM). However, all these SEC methods require a large amount of interpolation computation, and often consume much time, and therefore are often believed to be less efficient. Such SEC methods are usually applied for a first image of consecutive images, because the first image has no previous frame to refer to.
A further method proposed as another solution is called the TEC method. According to the TED method, a motion vector of a missing macroblock can be achieved by referring to a correct image data of a previous frame. Then, a reference frame is moved according to the motion vector, and therefore the image data of the missing macroblock can be thus obtained. In such a way, the negative affection to the entire image frame caused by the missing macroblock can be concealed.
In conventional TEC methods, a zero motion vector, neighboring motion vectors (motion vectors), an available motion vector of a spatially corresponding macroblock in a previous frame, or a median (or an average) of spatially adjacent motion vectors can be used. A TEC method called motion field interpolation method is recently proposed. According to the motion field interpolation method, a best motion vector is determined from the above candidate motion vectors by the boundary matching algorithm (BMA), which calculates the minimum sum of absolute differences (SAD) along the one-pixel-wide boundary between the missing macroblock and its candidate replacements in the H.264 JM decoder.
However, the conventional technology usually calculates an optimal motion vector by complex computation, which requires a large amount of computation and consumes much time, and negatively affects the overall decoding efficiency.
As such, an efficient TEC method which is demanded for obtaining decoded images while reducing the amount of computation, as a solution to the difficulty of the conventional technology.